4. At 25 °C, the values Keg and ASsurr for dissolving of sodium hydrogen carbona

Question

4. At 25 °C, the values Keg and ASsurr for dissolving of sodium hydrogen carbonate are given: (S points each) K 1042 Use the above information to find the following thermodynamic variables for this process: S surr--88.98 3/(mol K) For the reaction above, as T is increased, answer the following questions by sircling your choice: (2 points each) (a) Will more or less carbon dioxide form? (b) will AG increase or decrease? (c) Will ASsurr increase or decrease? (d) will ?Suniv increase or decrease? (e) ill Keg increase or decrease?

Explanation / Answer

Ans 4

Given that

K = 10.42

Gibbs free energy change of reaction

G° = - RT ln K

= - 8.314 J/mol·K x (25+273)K x ln 10.42

= - 5806.75 J/mol

= - 5.806 kJ/mol

H°sys/T = S°surr

H°sys = S°surr x T

= - 88.98 J/mol·K x 298K

= - 26516.04 J/mol

= - 26.516 kJ/mol

G° = H°sys - TS°sys

- 5806.75 = - 26516.04 - 298 x S°sys

S°sys = - 69.49 J/mol·K

S°univ = S°sys + S°surr

= - 69.49 - 88.98

= - 158.47 J/mol·K

Temperature at which the reaction becomes spontaneous

G° = H°sys - TS°sys

0 = - 26516.04 - T x (-69.49)

26516.04 = T x (69.49)

T = 381.58 K

T = 108.58 °C

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